What Is a Drive Rod?

The automatic control rod driving system is a mechanism that moves the control rod up and down or maintains it at a certain height. The main types are magnetic lifting type and reluctance motor type. The former is mostly used for onshore nuclear power plants, while the latter is mostly used for ship nuclear power plants. They all have the advantages of full sealing, fast falling rod reliability, etc. The magnetic lifting type has higher lifting force than the reluctance motor type, long life, simple structure, convenient processing, assembly, disassembly and maintenance. The advantages of the reluctance motor type are stable operation and vibration resistance. Strong sex.

The automatic control rod driving system is a mechanism that moves the control rod up and down or maintains it at a certain height. The main types are magnetic lifting type and reluctance motor type. The former is mostly used for onshore nuclear power plants, while the latter is mostly used for ship nuclear power plants. They all have the advantages of full sealing, fast falling rod reliability, etc. The magnetic lifting type has higher lifting force than the reluctance motor type, long life, simple structure, convenient processing, assembly, disassembly and maintenance. The advantages of the reluctance motor type are stable operation and vibration resistance. Strong sex.

Chinese name

Automatic control rod drive system

Foreign name

control rod drive mechanism

Introduction of automatic control rod drive system

Magnetic lifting control rod driving mechanism

A mechanism for lifting and lowering a control rod by using electromagnetic force and quickly lowering the control rod by gravity. The mechanism is generally composed of five components: a driving rod component, a claw component, a pressure-resistant shell component, a yoke component, and a rod position indicating component. It is installed on the reactor cover of the pressure vessel top cover. It is threadedly connected to the pressure vessel tube seat through the sealing shell of the pressure-resistant shell part, and is welded with seal. The special seal cutter and welding machine are used for automatic cutting during assembly and disassembly And welding. The three working coils (lifting coil, transfer coil, holding coil) of the yoke part are cooled with forced air; the pressure shell is filled with reactor coolant. The yoke part is sleeved on the outside of the sealed case. When three working coils pass DC power according to the design procedure, the three pairs of magnetic poles and armature installed in the sealed case are induced and attracted accordingly, driving the two sets of hooks and the ring rod of the driving rod part The upper grooves engage alternately, causing the drive lever member to move up or down one step at a time. The flexible joint of the driving rod component is connected with the connecting handle of the control rod bundle assembly, and is disassembled by special tools. The axial position of the control rod bundle assembly in the reactor is indicated by the rod position indicator part and its indicating instrument (light display and digital device) sleeved outside the position indicating inner casing. When all three working coils are powered off, the control rod quickly falls into the core by gravity, and the control rod is buffered in the buffer section of the guide tube.

Reluctance motor type control rod driving mechanism

A reluctance motor of the synchronous motor type is used to drive the roller screw to raise and lower the control rod. Stepless speed regulation in the range of 0 ~ 80r / min is performed by a variable frequency power supply to adjust the rising and falling speed of the control rod. When the power is cut off, the roller opening and closing nut is loosened under the action of the spring, and the control rod is rapidly lowered by the weight of the spring and the acceleration of the spring force. This driving mechanism is composed of a screw rod component, a split rotor component, a pressure-resistant casing, a stator component, and a rod position indicating component. The transmission of the screw rod and roller opening and closing nut is smooth, but because of the complex structure of the split rotor and high temperature bearing, the life of the mechanism is short. This drive mechanism is commonly used in ships' power reactors.

Because the control rod is in contact with the reactor coolant, the parts are required to be made of corrosion-resistant metal. Commonly used are stainless steel, nickel-chromium-iron alloy, and cobalt-based alloy.

The automatic control rod drive mechanism needs to pass the verification test and acceptance test to meet the design parameter requirements. The device's equipment rating is safety level 3, and its pressure shell components are reactor coolant pressure boundaries, and are safety level 1 components. The mechanism belongs to earthquake-resistant Class I equipment.

/ Automatic control rod drive system control rod lifting / lowering program

Control stick lifting procedure

The lifting coil is energized, the gap between the lifting magnetic pole and the lifting armature (equal to the step distance) is closed, and the control rod is lifted by one step (generally 10mm or 15.9mm);

The transfer coil is energized, the transfer claws are turned into the grooves of the ring rod to fit the tooth surface, and then the ring rod is lifted (usually about 1mm to reduce wear). The claws are transferred to the transfer hooks;

Keep the coil off and keep the claws turning out of the groove of the ring rod;

The lifting coil is de-energized, and the hook is lowered one step to the next groove position adjacent to the original groove of the ring rod;

Keep the coil energized and keep the claws turned into the groove of the ring rod. At this time, there is an axial gap between the upper and lower tooth surfaces (typically about 1mm to reduce wear);

The transmission coil is de-energized, and the transmission hook is turned out of the groove of the annular rod, and the load falls on the holding hook. At this point, the control rod completes the step of lifting one step. Repeat the above sequence, the control rod is lifted step by step to the required height.

Control stick descent procedure

The transfer coil is energized, the transfer hook is transferred into the groove of the ring rod and fits with the tooth surface, then the ring rod is lifted, and the load is transferred from the holding hook to the transfer hook;

Keep the coil off and keep the claws turned out of the groove of the ring rod;

The hoisting coil is energized to keep the claws raised by one step under no-load conditions;

Keep the coil energized and keep the claws turned into the groove of the ring rod. At this time, there is an axial gap on the upper and lower tooth surfaces.

The transmission coil is de-energized, and the transmission claw turns out of the groove of the ring rod, and the load falls on the holding claw;

The lifting coil is de-energized, and the hook is lowered by one step with the load. At this point, the control rod completes the process of one step down. Repeat the above sequence, the control rod is lowered step by step to the required height.